Phenylbutazone Pharmacokinetics and Bioavailability in the Dromedary Camel (Camelus Dromedarius)

Abstract

Phenylbutazone was administered intravenously and intramuscularly at a dosage rate of 4.4 mg/kg to a group of 6 female camels in a two-period crossover study. After intravenous (i.v.) administration, disposition was characterised by a two-compartment open model, with a low volume of distribution (0.174 l.kg-1), and distribution and elimination half-lives of 0.43 and 12.51 h, respectively. After intramuscular (i.m.) dosing absorption was relatively rapid with absorption half-time and time of maximal concentration values of 1.14 and 3.95 h, respectively. Plateau concentrations of phenylbutazone in plasma were obtained between 2 and 12 h and mean bioavailability was 97%, although this was subject to wide inter-animal differences. Plasma concentrations of the phenylbutazone metabolite, oxyphenbutazone, were low after iv dosing and generally undetectable after im administration, indicating that it is unlikely to contribute significantly to the pharmacological effects produced by phenylbutazone administration. An indication was obtained that phenylbutazone inhibited the ex vivo synthesis of serum thromboxane B2 (TxB2) for 24h after i.v. dosing, but this finding requires confirmation.

Pharmacokinetics of phenylbutazone in llamas following single intravenous and oral doses

“…administration were approximately 2 h and 67 mL/h/kg, respectively, which are between values found in horses and donkeys (Lees & Higgins, 1985; Maitho et al ., 1985; Cheng et al ., 1996; Mealey et al ., 1997). We can hypothesize that as the volume of distribution in llamas was similar to other species, that the protein binding is also high in llamas as it is in other species (Eberhardson et al ., 1979; Soma et al ., 1983; Eltom et al ., 1993; Cheng et al ., 1996; Kadir et al ., 1997). Further studies are needed to verify the concentration of protein binding, and determine what roles renal excretion and hepatic metabolism have in the high clearance and short half‐life of phenylbutazone in llamas.…”

Enantiospecific pharmacokinetics and pharmacodynamics of ketoprofen in sheep

“…Concentrations of serum TxB 2 with the placebo treatment were lower (8.6–16.46 ng/mL) than those reported in other species, such as calves (> 100 ng/mL) ( Landoni et al ., 1995a ; Landoni & Lees, 1995b) and horses (75–100 ng/mL) ( Landoni & Lees, 1995a, 1996). Synthesis of TxB 2 is species‐specific, being extremely low in some species such as the camel ( Kadir et al ., 1997 ).…”

Comparative Pharmacokinetics of Theophylline in Camels (Camelus dromedarius) and Goats (Caprus hircus)

“…It has also been reported that the hepatic capacity to clear caffeine from the systemic circulation is similar between sheep and cattle, but that the preferred routes of metabolism differ; the predominant metabolite being theophylline in sheep, and parathanxine in cattle (Danielson and Golsteyn, 1996). In another study, camels, unlike horses, were found not to biotransform phenylbutazone to oxyphenbutazone to any appreciable extent (Kadir et al., 1997). We have also previously found that camels metabolize and excrete the diuretic drug furosemide at a rate significantly slower than that in horses (Dyke et al., 1996; Ali et al., 1998).…”